1. Field of the Invention
The present invention relates to a punch and die device for working a pipe material. In particular, it relates to a punch and die device comprising improved inner die means which is inserted and placed in a pipe in working operation.
2. Description of the Prior Art
As heretofore, in working of a pipe material such as punching, working is performed by cooperation between external punch means located outside the pipe material and internal die means inserted and placed in the pipe material.
Conventional internal die means inserted and placed in a pipe material P include one which comprises, as shown in FIG. 11, mechanisms for pushing one p2 of sides lateral relative to a side p1 to be worked of the pipe P by means of balls 64 biased with forces of springs 63 to thereby position the internal die means with a punch 30 of upper or external punch means and a die D of the lower or internal die means in alignment with each other. In FIG. 11, reference number 61 is an upper block of the internal die means and reference number 62 is a lower block of the same.
However, such conventional internal die means has a problem as follows. To be capable of pushing the one p2 of the sides of the pipe material P which are lateral relative to the side p1 to be worked by means of the balls 64 biased with the forces of the springs 63, the internal die means to be inserted necessarily has an outer dimension which is larger as compared with the inner dimension of the pipe material P between the side p2, on which the balls 64 abut, and the side p3 opposite thereto. Accordingly, it is not easy to insert the internal die means into the pipe material P from an open end of the pipe material P, and a strong force is required for the insertion. In particular, if the open end has burrs inward extending therefrom, the insertion becomes further difficult.
The conventional device has another problem as follows. The positioning of the internal die means is performed under the forces of the springs 63 and the actions of the balls 64, as described above. Accordingly, if any operational failure is caused in the balls 64, it is difficult to detect the condition. Further, the positional relationship between the working portion (die) of the internal die means inserted in the pipe material P and the pipe material P is determined according to the distance from the one side of the inner surface of the pipe material P to the working portion (die). Accordingly, in a case where it is required to work a pipe material P at a position on the center line of the pipe material P with respect to the width direction, if there are variations in widths of pipes P, it is not possible to effect working which satisfies the requirement with respect to every pipe P.